PIEZOCOMPOSITES OF COMPLEX MICROSTRUCTURE - THEORY AND EXPERIMENTAL ASSESSMENT OF THE COUPLING BETWEEN PHASES

A new theoretical framework is presented for the study of the elastic, dielectric, and piezoelectric properties of two-phase piezoelectric c omposite materials of complex microstructure. These kinds of materials are usually analyzed by means of averaging models. This paper begins with basic thermodynamic relations and obtains new general constitutiv e equations for a two-phase composite. These new constitutive equation s consider in a general and novel way the dielectric and elastic inter actions between the two components and provide a method of measuring o r calculating these interactions, as well as their influence on the gl obal behavior of the composite. Some measurements of the dielectric, m echanical, and piezoelectric properties of 3-3 and 0-3 composites are presented and compared with the results of both this new approach and an averaging model.